January 4, 2011
Walking six or more miles per week may keep memory sharp in old age, new research suggests. Seniors who walked at least six miles a week had more brain gray matter than their more sedentary peers, and more gray matter has been linked to a lower risk for memory and thinking problems. The findings add to a growing body of evidence that steady exercise and regular aerobic activity, like walking and dancing, is good not just for cardiovascular health but for the brain as well.
“Brain size shrinks in late adulthood, which can cause memory problems,” said researcher Kirk I. Erickson, Ph.D., of the University of Pittsburgh. “Our results should encourage well-designed trials of physical exercise in older adults as a promising approach for preventing Alzheimer’s disease.”
The study, part of the ongoing Cardiovascular Health Study, involved 299 men and women living in urban areas. Their average age was 78, and all were free of Alzheimer’s or serious memory problems. At the study’s start, researchers recorded the typical number of blocks they walked in a week.
Nine years later, the scientists took brain scans of the participants to measure their brain size. After four more years, the participants were tested to see if they had developed signs of Alzheimer’s or other forms of dementia.
The researchers found that people who walked at least 72 blocks per week, or roughly six to nine miles, had greater gray matter volume than people who didn’t walk as much. Walking more than six miles did not appear to be associated with further increases in brain volume.
After four years 116 of the participants, or 40 percent, had developed serious memory problems or other symptoms of Alzheimer’s. The researchers found that those who walked the most had half the risk of developing memory problems compared to less active participants. Many researchers and doctors believe that exercise is likely to reduce the risk of Alzheimer’s disease. However, the current study, like most others of its kind, relies on observing groups of people but the participants were not randomly assigned to each group. As a consequence it cannot be ruled out that those who walked more did so because they were the most fit and some aspect of their fitness other than the actual walking exercise resulted in lower dementia risk. In other words, we don’t know whether walking caused the reduced risk or whether something else common to walkers was the cause.
Earlier research has shown that regular exercise helps protect against deterioration of brain tissue in the hippocampus and other areas critical for memory and may protect against Alzheimer’s and other types of dementia. And in mice that have been bred to develop an Alzheimer’s like illness, rigorous exercise diminishes the buildup in the brain of the beta-amyloid plaques and tau that characterize the disease in people.
Conversely, couch potatoes and those who rarely work out are at increased risk for Alzheimer’s.
It may be especially important to exercise early in life, given mounting evidence that Alzheimer’s risk can be cut by exercise during midlife. But walking and other activity may provide benefits at any age, the findings suggest.
“If regular exercise in midlife could improve brain health and improve thinking and memory in later life, it would be one more reason to make regular exercise in people of all ages a public health imperative,” Dr. Erickson said.
Source: K. I. Erickson, C. A. Raji, O. L. Lopez, et al: “Physical Activity Predicts Gray Matter Volume in Late Adulthood.” Neurology, Oct. 13, 2010.